Real-world listening situations are complex and dynamic, often requiring us to tune out irrelevant auditory information. Understanding how the auditory system tackles this challenge is stifled by the constraints of current laboratory-based recording techniques. This study aims to overcome these constraints and develop better metrics of communication abilities under real-world listening conditions by using a new methodology that simultaneously measures auditory cortical and brainstem evoked responses during a selective attention task. It follows a growing trend of using a fewer stimulus presentations and natural stimuli (i.e., sentences) to evoke auditory brainstem responses. Online measures will be recorded during a task involving selective attention to two competing voices, mimicking the common daily experience of perceiving speech in noisy conditions. While many with normal auditory function can do this task with ease1, the ability to segregate two competing auditory streams is a daily challenge faced by many clinical populations2,3 and older adults4,5. Therefore, in an effort to pinpoint potential biomarkers of remediation, we seek to understand which aspects of auditory function are sensitive to experience and if this experience-dependent plasticity influences auditory perception during listening situations that require separating a target signal from noise (i.e., competing, irrelevant signals). Experience-dependent plasticity wil be assessed by testing bilinguals, a population known to have superior selective attention skills6-9, and monolinguals. This study is motivated by recent evidence that (a) the acoustic features of an attended speech sound are represented in the cortical response while the irrelevant stream is suppressed (when responses are measured by a multi-electrode array on the surface of the cortex) and (b) the auditory brainstem and cortex are sensitive to both the acoustic features of a stimulus and experience with that sound10-14 even under passive listening conditions8,9,15. From this evidence we hypothesize that the brainstem is dynamically involved in real-world listening situations and that the changes in the auditory brainstem response as a result of selective attention will pattern with attention-induced changes in cortical processing. Additionally, we predict that experience influences both selective attention and sensory processing during real- world communication. To test this, we will simultaneously record, using scalp electrodes, auditory brainstem responses and cortical responses as participants are actively attending to one of two competing talkers. We predict that selective attention will enhance both the brainstem and cortical responses to an attended talker and suppress the brainstem and cortical responses to an ignored talker. We predict that auditory experience will change the effect of selective attention on auditory processing, with greater auditory diversity through bilingualism leading to a greater effect of selective attention on auditory processing6,8,9. This study will improve our knowledge of the biological mechanisms engaged during more realistic listening conditions than typically employed in the laboratory and will identify aspects of auditory processing that may benefit from remediation.